01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Bring a large pot of salted water to a boil. Add cauliflower florets and cook for 4 minutes. Add pasta and cook both together for 5–6 minutes, until pasta is al dente and cauliflower is just tender. Drain well and set aside.
03 - In a medium saucepan, melt butter over medium heat. Whisk in flour to form a roux; cook for 1–2 minutes until bubbling but not browned, stirring constantly.
04 - Slowly whisk in milk, stirring constantly until sauce thickens, about 4–5 minutes. The sauce should coat the back of a spoon.
05 - Remove from heat. Stir in cheddar, mozzarella, Parmesan, garlic powder, onion powder, smoked paprika, salt, and pepper until completely smooth and melted.
06 - Combine cooked pasta and cauliflower with the cheese sauce. Mix thoroughly to coat evenly and transfer to the prepared baking dish.
07 - In a small bowl, toss breadcrumbs with Parmesan and olive oil until well combined. Sprinkle evenly over the top of the pasta mixture.
08 - Bake for 20–25 minutes, or until bubbling and golden brown on top. Let rest for 5 minutes before serving to allow the sauce to set.